For example, for a disk array device including a plurality of hard-disk drives, write data is divided and written to the plurality of hard-disk drives, and data read from the hard-disk drives are combined together and output as data to be read. In such a disk array device, when the frequency of accesses becomes lower than a threshold, power supply to one or some of hard-disk drives is stopped, and data is written to the hard-disk drives for which the power supply is maintained, without being divided (for example, see Japanese Laid-open Patent Publication No. 2002-297320).
There is also a proposed scheme for reducing the power consumption by controlling execution of a task and power supply of a storage device based on, of schedule plans for executing tasks using a storage device, a schedule plan that satisfies a predetermined condition (for example, see Japanese Laid-open Patent Publication No. 2009-48583).